This invention relates to television systems. Specifically, this invention relates to methods and devices for adaptively placing overlay elements in videos.
During the production and display of television broadcasts, the images of the video can have various elements overlaid across areas thereof. A typical example of such an overlay element is a closed captioning window, which is usually positioned on the bottom or top of the image. Other overlay elements may include captions for the displayed persons, scoreboards, news tickers, logos etc.
The exact location of the overlay element in the image is usually random and often blocks areas of the image that may be highly desired by viewers to see, such as text or human faces. This is due to the fact that in the analog domain, there are no practical techniques for detecting semantic features and adaptively adjusting the placement of the overlay element in the images.
Consequently, in the case of a closed captioning window, the placement thereof at the bottom or the top of the image is currently made in a manual selection process. As a result, especially in live broadcasts, the closed captioning window or other overlay material or objects is often overlaid across desirable areas of the image thereby occluding (blocking) the same.
Methods and devices are, therefore, needed for adaptively placing overlay elements in images of videos so that the desirable areas of the images are not occluded thereby.
In accordance with one aspect of the invention, a method for placing overlay elements in images of a digital video so that desirable viewing areas of the images are not occluded thereby, comprises extracting frames from the video, each of the frames defining an image which may have one or more desirable viewing areas which may be identified by detecting face or text, or measuring motion activity in different areas of the frames. For each frame, an area is selected in the image for placing the overlay element and the percentage the overlay element overlaps the desirable viewing areas is determined for the selected area. The selected area may be a randomly selected position in one of a plurality of predetermined positions. The overlay element is placed in the selected area if the percentage is below a maximum allowed predetermined percentage of overlapping. If it is not, one or more other areas in the image are selected and evaluated as described above until an area is found which minimizes occlusion of the desirable viewing areas in the image. These other areas may be one of the other predetermined positions or positions selected using some other selection scheme. Alternatively, the occlusion can be minimized by changing the size, shape, aspect ratio, and/or the like of the overlay element instead of changing its position in the frame. Additionally, occlusion can be minimized by changing the position of the overlay element while simultaneously changing the size, shape, aspect ratio, and/or the like of the overlay element.
In accordance with another aspect of the invention, a device, such as a video transmitter or video receiver, for placing an overlay element in images of a digital video so that desirable viewing areas of the images are not occluded by the overlay element, comprises a frame extractor for extracting frames from the video, each of the frames defining an image which may have at least one desirable viewing area that may be identified by detecting face or text, or measuring motion activity in different areas of the frames. An image processor analyzes the images of the frames to identify desirable viewing areas in the images of the frames. An overlay element locator places the overlaid element in the images of the frames in a manner which minimizes the occlusion of the desirable viewing areas.